1. Field of the Invention
The present invention relates to a method for fabricating an active device array substrate, and particularly to a method for fabricating an active device array substrate which reduces a number of photolithography and etching processes (PEPs) required.
2. Description of Related Art
Generally, a conventional method of fabricating a pixel structure of a liquid crystal display (LCD) panel includes five photolithography and etching processes (PEP). The first PEP is used to define a pattern of a first metal layer, so as to form a scan lines and gate electrodes of an active device. The second PEP is used to define patterns of a channel layer and an ohmic contact layer of the active device. The third PEP is used to define a pattern of a second metal layer, so as to form data lines and a source electrode and a drain electrode of the active device. The fourth PEP is used to pattern a passivation layer above the second metal layer, so as to form a contact window in the passivation layer. The fifth PEP is used to pattern an electrode material layer, so as to form the pixel electrode.
In order to enhance display quality of LCDs, many LCDs incorporate photo-sensors which sense light. Generally, photo-sensors integrated in LCDs are usually used to sense ambient light, so that the LCDs adequately adjust displayed brightness according to intensities of ambient light while displaying. In another application, the photo-sensor may be used as a sensing device of an optical touch panel. When a user uses a finger or another object (such as a stylus) to touch the optical touch panel, the photo-sensor integrated in the LCD panel senses changes in the intensity of light and outputs corresponding signals to provide touch functions. Under circumstances where the photo-sensors are disposed densely enough, the photo-sensors may be used in fingerprint identification and image scanning.
In recent years, disposition of photo-sensors have become gradually integrated in the LCD panels. However, when the photo-sensors are to be fabricated on the active device array substrates, PEP number required during fabrication increases, thereby lowering competitiveness of products.